The background of this invention pertaining to detecting discontinuities in a flowing fluid stream in a narrow conduit is fully set out in my U.S. Pat. Nos. 4,112,773 and 4,214,484, both hereby incorporated by reference.
In addition to obtaining information about fluids flowing in conduits, however, it is also desirable to be able to obtain such information about large volumes of fluids standing in or slowly circulating through large containers.